Women who get lots of omega-3 fatty acids are less likely to develop age-related macular degeneration (AMD), an eye disease affecting millions of older adults in the U.S.
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That's the conclusion of a new study, which fits with earlier research linking fish consumption to slower progression of AMD. Fish rich in omega-3 fatty acids such as DHA and EPA include salmon, trout, sardines, herring and tuna.
AMD is caused by abnormal blood vessel growth behind the retina or breakdown of light-sensitive cells within the retina itself -- both of which can cause serious vision impairment. Some 1.7 million Americans have severe vision loss due to the disease, making it the leading cause of blindness in older adults.
At this point, doctors can halt AMD, but they can't reverse damage to the retina. So researchers have been busy looking for ways to stave off the disease.
"Other than giving up cigarette smoking or never starting smoking, there are no known ways to prevent AMD," said William G. Christen of the Brigham and Women's Hospital in Boston, who worked on the new study, published in the Archives of Ophthalmology.
Christen and colleagues used data from earlier research called the Women's Health Study, in which women 45 years and up had filled out extensive diet questionnaires.
After 10 years, 235 out of 38,022 women had developed AMD severe enough to damage their vision.
When the researchers looked at all food sources of the important fatty acids, the risk of AMD was 38 percent lower in women with the top one-third DHA intake compared to those with the bottom one-third intake. For those who got a lot of EPA, the risk was 34 percent smaller.
"We also looked at the food intake of (just) fish and the data were consistent there," said Christen, also of the Harvard Medical School.
He pointed out, however, that it is too early to recommend that people start supplementing their diet with fish or with fish oil supplements to stave off eye disease.
That's because the study was based on observations, not on a real experiment, and so it can't rule out that women who got lots of omega-3s were simply healthier people.
"It supports the need for randomized clinical trials," said Christen. "The best advice we have at this point is, don't smoke."